The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A critical challenge in nanocomposite fabrication is the ability to realize materials that allow the transfer of the exceptional mechanical properties i.e. tensile strength, σUTS, and Young's modulus, E, of the nanoscale materials to the macroscale properties of the bulk materials. Nanoparticle-filled polymer composites based on these structural elements have mechanical properties that fall far below the expected theoretical and experimentally determined values of the individual building blocks, except at low reinforcement volume fractions. The deficiency in the properties of the composite is largely related to the difficulty of obtaining well-dispersed large volume fractions of the reinforcing nanomaterials and a lack of structural control. The difficulty is also associated with realizing an effective load transfer from the polymeric matrix to the nanoscale components and the insufficiently understood mechanical interactions of the two constituents at the nanoscale. We demonstrate that it is possible to produce composites with properties that approach the theoretical maxima using spatial and orientational control of clay platelets in a polymer matrix at the nanoscale and retaining this order at the macroscale.
Hybrid organic-inorganic nanocomposites of polymer and clay nanoplatelets have received special attention because of the very low cost of the inorganic component, relatively simple preparation, and fairly predictable stiffening behavior when introduced into polymers. Montmorillonite clay (MTM ˜1 nm thick by 100-1000 nm diameter sheets), has been extensively used for this purpose because it is readily available and has exceptional mechanical properties. The in-plane modulus of elasticity has been estimated by Monte Carlo simulations to be ˜270 GPa. While composites incorporating 50 vol. % of MTM should theoretically have stiffness values on the order of 100 GPa, values achieved to date with MTM platelets are at least an order of magnitude lower. This is because in general less than ˜10 wt. % of clay can be incorporated homogeneously as completely dispersed silicates rather than intercalated structures into the polymer due to the strong tendency of the clay to aggregate and phase separate. Further increases in the volume of clay content have either marginally increased or even reduced both the strength and stiffness.